Increasing use of solar energy for water heating has prompted many innovations in the design of solar collectors and headers on the one hand and low cost heat exchangers on the other, but relatively little attention has been given to energy-efficient conduit designs for thermal transfer between them. The present invention is the result of efforts to provide a less expensive alternative to conventional rigid or flexible piping, whether plastic or metal. Various forms of foam insulation for hot waterpiping have long been known, such as sleeves installed in the field, but they are far from ideal in cost and thermal efficiency. There have been some versions of composite multi-tube foam insulated conduits, for example U.S. Pat. No. 3,747,632, but none has involved a unitary extrusion wherein primary tubes are spaced apart by an integral intermediate section separable from the primary tubes along tear lines.